This invention relates to a solution of crystalline polymers in halogenated diphenyl ethers. In one of its aspects, this invention relates to a solution of polyarylene sulfides in such ethers.
Many crystalline polymers dissolve slowly or only to a relatively low percentage in common organic solvents. In particular, crystalline polyarylene sulfides have heretofore been known to be nearly insoluble in common organic solvents. The insolubility of polyarylene sulfides has created considerable difficulty in purification and solvent casting of these polymers.
It is known in the art that crystalline, linear polymers of arylene sulfides are slightly soluble, i.e., to a weight concentration of about 2 percent, in diphenyl ether at about 200.degree. C. Dow Chemical Company Technical Data Sheet on QX 4375.1 (1964). U.S. Pat. No. 3,317,487 discloses that polyphenyl compounds are suitable and chlorinated biphenyl compounds preferred as solvents for polyarylene sulfides. The best known solvents for the polyarylene sulfides are reported in Encyclopedia of Polymer Science and Technology, Vol. 10, p. 656 (1969) to be chlorobiphenyl (PCB) solvents. The use of chlorobiphenyl compounds has recently been restricted for environmental reasons.
In view of the deficiencies in the aforementioned prior art solvents for polyarylene sulfides, it would be highly desirable to provide a solvent and a method for dissolving polyarylene sulfides which are not tainted with controversy regarding the environmental hazards of such a solvent and which dissolve an appreciable amount of such polymer. Furthermore, it would be desirable to provide a new solvent and method for dissolving other highly crystalline polymers in appreciable amounts.